Two speed hoist for earth-moving vehicle



Jan. 2, 1968 Filed July 27, 1965 J. A. BEDNAR- ETAL 3,360,875

TWO SPEED HO IST FOR EARTH-MOVING VEHICLE 2 Sheets-Sheet 1 W INVENTORS dosepfi C2 Bea 27m 5 BY (Y/V/i? Q 9700:!

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ATTORNEY Jan. 2, 1968 J BEDNAR ETAL 3,36

TWO SPEED HOIST FOR EARTH-MOVING VEHICLE Filed July 27, 1965 2 Sheets-Sheet 2 ATTORNEY United States Patent 3,360,875 TWO SPEED HOIST FOR EARTH-MOVING VEHICLE Joseph A. Bednar, North Olmsted, and Alvin A. Rood,

Willoughby, Ohio, assignors to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed July 27, 1965, Ser. No. 475,150 Claims. (Cl. 37-129) This invention concerns a hydraulic circuit for an earth-moving vehicle and more particularly a hoist or jack which is used for raising and lowering an earthworking implement.

One form of scraper presently being marketed commercially has the bowl supported by a lever arrangement which includes a jack that is attached at one end to the pull arms. The jack is of the single-acting type and is located in a hydraulic circuit which provides for pressurization and quick venting of the piston head end of the jack for respectively raising the bowl and fast dropping of it by gravity. Although this system has proven to be highly successful it has been found that there are times when it would be desirable for the circuitry to provide a slow drop of a loaded bowl in addition to a fast drop.

Accordingly, the objects of the present invention are to provide a jack that can lower an earth-working implement by gravity at two different speeds; to provide a hydraulic circuit for controlling the operation of a jack so that fluid can flow from one end to the other end of the jack at two different flow rates; to provide a jack in which suitable valving is incorporated with the piston for permitting fluid to flow from one end of the jack to the other; and to provide a hydraulic system in which pressurized fluid located at one end of a jack is utilized for actuating valving which controls the flow of fluid between the opposite ends of the jack.

The above objects and others are accomplished in accordance with the invention by an arrangement that is specifically described below and illustrated in the accompanying drawings in which:

FIGURE 1 shows a scraper equipped with a hoist incorporating the subject invention;

FIGURE 2 shows the hydraulic circuitry utilized for controlling the movement of the hydraulic cylinder incorporated with the scraper of FIGURE 1; and

FIGURE 3 is a sectional view showing in detail the construction of a hydraulic cylinder made in accordance with the invention.

Referring to the drawings and more specifically FIG- URE 1 thereof, a scraper 10 of the type alluded to above is shown comprising a tractor 12 which supports a gooseneck 14 that extends rearwardly for connection with the usual pull arms, one of which is indicated by the numeral 16. The rear end of the pull arms pivotally supports a trailing bowl 18 which is adapted to be raised and lowered through a lever arrangement 20 which includes a bellcrank 22, one arm of which is connected to the piston rod end of a hoist or jack 24. The other arm of the bellcrank 22 is pivotally connected to a link 26 that extends downwardly for pivotal connection with the front end of the bowl 18. The jack 24 is of the single-acting type so that upon pressurization of the piston head end thereof the bellcrank 22 is rotated counterclockwise about its pivot connection 28 to raise the bowl 18. To lower the bowl 18, fluid from the piston head end of the jack 24 is vented in a manner to be described so that the bowl can fall to the ground by gravity.

At this juncture, it will be noted that although the subject invention is described and illustrated in connection with a scraper it will be understood that it can be utilized with other forms of earth-working implements such as a "ice dozer blade. It will be further noted that although the scraper 10 is shown employing only one jack and lever arrangement 20 for raising the bowl, it has in fact identical components similarly located on the opposite side with the two jacks suitably interconnected so that their movements are synchronized.

Referring now to FIGURES 2 and 3, the jack 24 is shown comprising relatively movable piston and cylinder members 30 and 32 suitably incorporated with a hydraulic circuit which controls expanding and contracting movement of the jack. This hydraulic circuit comprises a control valve 34 which receives pressurized fluid through a line 36 from a pump 33 which in turn is connected through a line 40 to a tank 42 containing hydraulic fluid. The control valve 34 contains the usual spool valve (not shown), the position of which is controlled by a lever 44 having positions L, H and R which correspond to the lower position, hold position, and a raised position, respectively. When the spool valve is in the hold position, the fluid being directed to the control valve 34 by the pump 38 is simply recirculated back to the tank 42 through a line 46. In the R or raised position, pressurized fluid is directed through a line 48 to port 47 in the piston head end of the jack 24 while fluid from the piston rod end of the jack is returned to tank 42 through a port 49 and lines 50 and 46. In the L or lower position, the port 49 is also connected to tank 42 through lines 50 and 46. The control valve 34 is of the conventional design and consequently details thereof are not deemed to be necessary.

It will be noted that in addition to the control circuit explained above an auxilary control 52 is provided having a lever 54 which can be moved between positions indicated by the letters FD, N, and SD which respectively represent fast drop, neutral and slow drop positions. The auxiliary control 52 is mechanically connected to the lever 44 of control valve 34 so whenever the lever 54 is in the FD or SD position, the lever 44 is automatically moved to the L position. The control 52 is also electrically connected through a relay 56 to a pair of identical solenoid valve assemblies 58 and 60. Each of the valve assemblies includes a body portion 62 having a vertically extending bore 64 which rigidly supports a sleeve member 66. The bore 64 connects with transverse and vertically spaced ports 68 and 70 which respectively are connected by pilot lines 72 and 74 to a port 75 at the piston head end of the jack 24 anda port 76 located in the eye mounting of the piston member 30. In the valve assembly 58, the port 80 corresponding to port 68 in valve assembly 60 is also connected by a branch line 82 to port 75 in the jack 24. However, the port 84 corresponding to port 70 in valve assembly 60 is connected through a line 86 to another port 78 located in the aforementioned eye mounting.

Each valve assembly 58 and 60 also has a spool valve 88 slidably located within the sleeve member 66 and formed with an enlarged annular land 90 at the lower end thereof which leads into a reduced portion 92 terminating with a shoulder 94. The spool valve 88 is adapted to move between the positon shown and a raised position wherein the land 90 serves to block the lower opening in the sleeve 66 and at the same time provide communication between ports 68 and 70 through the radially extending ports 95 and 98 formed in the sleeve member 66. Thus, in the position shown in FIGURE 2, the ports 96 are blocked by the spool valve portion above the shoulder 94. Therefore, energization of the coil 100 causes the armature 102 to rise and carry with it the rigidly attached spool valve 88. Moreover, deenergization of the coil results in the valve 88 reassuming its original position under the influence of the coil spring 104. As will become more apparent as the description of the invention proceeds, depending upon which of the valve assemblies is energized will determine the speed at which the jack 24 is contracted for lowering the bowl 18.

As best seen in FIGURE 3, the piston member 30 comprises a piston head 166 that is fixedly secured to one end of a tubular rod 108, the other end of which is rigid with the mounting eye having ports 76 and 78 formed therein. The piston head 106 is provided with a stepped bore 110 which supports a pair of sleeve members 112 and 114 held in fixed relative positions by a screw 116 having a central opening 117. The piston head is also formed with a plurality of circumferentially spaced radial ports 118 which lead into an annular chamber 120. The chamber 120 is connected by radial ports 122 to a longitudinal passage 124 provided in the sleeve member 112 and normally blocked by a spring biased check valve 126. The check valve is adapted to be opened so as to establish fluid communication between the piston and rod end of the jack by an actuator assembly 128 located in the sleeve member 114. The actuator assembly includes a primary plunger 130 and a secondary plunger 132, both of which are supported for axial movement relative to the sleeve member 114. As seen, the primary plunger 130 has an integral projection 134 which engages the check valve 126 and is adapted to be moved to open the latter a predetermined distance as limited by the end 136 of the sleeve member 112. The secondary plunger 132 has a radially slotted ring 138 that engages the rear of the primary plunger 130 and forms a fluid chamber 140 therebetween. Axial movement of the secondary plunger 132 is also limited by a shoulder 142 and it will be noted that the extent of permitted movement of plunger 132 is significantly less than the predetermined amount provided for the plunger 130. Thus, axial movement of the primary plunger 130 causes the check valve 126 to open a much greater amount than that provided by the movement of the secondary plunger 132. It will also be noted that a fluid chamber 144 is located to the'rear of the plunger 132 and is formed by a dead-end bore in the latter.

The rear end 146 of sleeve member 114 is connected with the piston rod eye mounting through a pair of elongated concentric tubes 148 and 150 which serve to define an annular passage 152 which connects with chamber 146 through passages 154, 156, 158, and a passage 160 which leads to the chamber 144. The passages 152 and 166 are respectively connected with ports 76 and 78 which, as aforementioned, are connected to the lines 74 and 86 leading to the solenoid valve assemblies. Thus upon pressurization of passage 152, the primary plunger 130 will move axially to the left, as viewed in FIGURE 3, to open the check valve 126 a predetermined amount as described above. Similarly pressurization of passage 160 causes the secondary plunger 132 to move the primary plunger 130; however, in this case, such movement is less than that provided by the primary plunger so that the check valve 126 is opened a lesser amount.

From the above, it should be apparent that when the bowl 18 is in the raised position of FIGURE 1 and the lever 54 is placed in the SD or slow drop position, the solenoid in the valve assembly 58 is energized causing the associated spool valve to move upwardly so that pressurized fluid at the piston head end of the jack 24 is directed to the port 78 via line 86. Accordingly, chamber 144 is pressurized and the secondary plunger 132 is moved, as described above, for limited opening of the check valve 126. The weight of the bowl acting on the piston head or lower end of the jack 24 causes the fluid to flow through the passage 124, radial ports 122, chamber 120, and ports 118 to the piston rod or upper end of the jack with resultant collapsing of the jack and lowering of the bowl. Inasmuch as the check valve opening is relatively small, the fluid moves at a relatively slow rate with consequent slow and controlled dropping of the bowl 18. On the other hand, when the lever 54 is placed in the fast drop or FD position, valve assembly 60 is energized and pressurized fiuid from port '75 is directed via lines 72 and '74 to port 76 and chamber 14% causing the primary plunger to move its full traveling distance and increase the opening of the check valve 126, as described above, with a resultant increase in flow of fluid between the opposite ends of the jack 24 and a fast dropping of the bowl 13. Thus, two speed rates are provided for lowering the bowl. To raise the bowl, the lever 44 is moved to the R position so that pressurized fluid generated by the pump 38 is directed through lines 48, port 47, and check valve 162 to the lower or piston head end of the jack 24; at the same time, fluid in the piston rod end of the jack 24- is vented through port 49 and lines 5%) and 46 to the tank 42.

Various changes and modifications can be made in this construction without departing from the spirit of the invention. Such changes and modifications are contemplated by the inventors and they do not wish to be limited except by the scope of the appended claims.

What is claimed is:

1. In combination, a hydraulic jack comprising relatively movable piston and cylinder members, said piston member having passage means formed therein for communicating the opposite ends of the cylinder, a spring biased check valve normally closing said passage means, an actuator assembly located in said piston member for moving said check valve to a first position wherein a predetermined flow rate between the ends of the cylinder is provided and to a second position wherein a flow rate greater than said predetermined flow rate is provided, said assembly comprising a primary plunger engaging the check valve and adapted to move said valve to said second position, a secondary plunger engaging the primary plunger and adapted to move the latter a distance whereby said valve is moved to said first position, and means for selectively activating said plungers.

2. In combination, a hydraulic jack comprising relatively movable piston and cylinder members, said piston member having passage means formed therein for communicating the opposite ends of the cylinder, a check valve normally closing said passage means, an actuator assembly for moving said check valve to a first position wherein a predetermined flow rate between the ends of the cylinder is provided and to a second position wherein a flow rate greater than said predetermined flow rate is provided, said assembly comprising a fluid actuated primary plunger engaging the check valve and adapted to move said valve to said second position, a fluid actuated secondary plunger engaging the primary plunger and adapted to move the latter a distance whereby said valve is moved to said first position, first and second conduit means provided in said piston member for respectively communicating pressurized fluid to one side of said primary and secondary plungers, and means for selectively pressurizing said conduits.

3. In combination, a hydraulic jack comprising relatively movable piston and cylinder members, said piston member having passage means formed therein for communicating the opposite ends of the cylinder, a spring biased check valve normally closing said passage means, an actuator assembly located in said piston member for moving said check valve to a first position wherein a predetermined flow rate between the ends of the cylinder is provided and to a second position wherein a flow rate greater than said predetermined flow rate is provided, said assembly comprising a fluid actuated primary plunger engaging the check valve and adapted to move said valve to said second position, a fluid actuated secondary plunger engaging the primary plunger and adapted to move the latter a distance whereby said valve is moved to said first position, first and second conduit means provided in said piston member for respectively communicating pressurized fluid to one side of said primary and secondary (plungers, and means for selectively pressurizing said conu1ts.

4. In combination, a hydraulic jack comprising relatively movable piston and cylinder members, said piston members having longitudinal passage means centrally formed therein and radially extending ports for communicating the opposite ends of the cylinder, a spring biased check valve normally closing said passage means, an actuator assembly located in said piston member in axial alignment with the check valve for moving the latter to a first position wherein a predetermined flow rate between the ends of the cylinder is provided and to a second position wherein a flow rate greater than said predetermined fiow rate is provided, said assembly comprising a fluid actuated primary plunger engaging the check valve and adapted to move said valve to said second position, a fluid actuated secondary plunger engaging the primary plunger and adapted to move the latter a distance whereby said valve is moved to said first position, first and second conduit means provided in said piston member for respectively communicating pressurized fluid to one side of said primary and secondary plungers, and means for selectively pressurizing said conduits.

5. In combination, a single acting hydraulic jack comprising relatively movable piston and cylinder members, said piston member having passage means formed therein for communicating the opposite ends of the cylinder, a spring biased check valve normally closing said passage means, an actuator assembly located in said piston member for moving said check valve to a first position wherein a predetermined flow rate between the ends of the cylinder is provided and to a second position wherein a flow rate greater than said predetermined flow rate is provided, said assembly comprising a fluid actuated primary plunger engaging the check valve and adapted to move said valve to said second position, a fluid actuated secondary plunger engaging the primary plunger and adapted to move the latter a distance whereby said valve is moved to said first position, first and second conduit means provided in said piston member for respectively communicating pressurized fluid to one side of said primary and secondary plungers, and control means or taking pressurized fluid from one end of said hydraulic jack and selectively pressurizing said conduits whereby the rate of contraction of the jack is varied.

6. In combination with an earth-moving vehicle having an earth-working implement movable between a raised and lowered position, a hydraulic jack supporting said implement for movement between said positions, said hydraulic jack comprising relatively movable piston and cylinder members, said piston member having passage means formed therein for communicating the opposite ends of the cylinder, a spring biased check valve normally closing said passage means, an actuator assembly located in said piston member for moving said check valve to a first position wherein a predetermined flow rate between the ends of the cylinder is provided and to a second position wherein a flow rate greater than said predetermined flow rate is provided, said actuator assembly comprising a fluid actuated primary plunger engaging the check valve and adapted to move said valve to said second position, a fluid actuated secondary plunger engaging the primary plunger and adapted to move the latter a distance whereby said valve is moved to said first position, first and second conduit means provided in said piston member for respectively communicating pressurized fluid to one side of said primary and secondary plungers, a hydraulic circuit for supplying pressurized fluid to one end of said jack whereby said implement is raised, said circuit including first and second valve assemblies between said pressurized end of said jack and said first and second conduits, and control means for selectively activating said valve assemblies whereby pressurized fluid from said pressurized end of said jack is directed to one of said conduits to cause said check valve to be opened so that the implement will drop by gravity.

7. In combination with an earth-moving scraper having 6 a bowl movable between a raised and lowered position, a hydraulic jack supporting said bowl for movement between said positions, said hydraulic jack comprising relatively movable piston and cylinder members, said piston member having passage means formed therein for communicating the opposite ends of the cylinder, a spring biased check valve normally closing said passage means, an actuator assembly located in said piston member for moving said check valve to a first position wherein a predetermined flow rate between the ends of the cylinder is provided and to a second position wherein a flow rate greater than said predetermined flow rate is provided, said actuator assembly comprising a fluid actuated primary plunger engaging the check valve and adapted to move said valve to said second position, a fluid actuated secondary plunger engaging the primary plunger and adapted to move the latter a distance whereby said valve is moved to said first position, first and second conduit means provided in said piston member for respectively communicating pressurized fluid to one side of said primary and secondary plungers, a hydraulic circuit for supplying pressurized fluid to one end of said jack whereby said bowl is raised, said circuit including first and second valve assemblies between said pressurized end of said jack and said first and second conduits, and control means for selectively activating said valve assemblies whereby pressurized fluid from said pressurized end of said jack is directed to one of said conduits to cause said check valve to be opened so that the bowl will drop by gravity.

8. In combination with an earth-moving vehicle having an earth-working implement movable between a raised and lowered position, a hydraulic jack supporting said implement for movement between said positions, said hydraulic jack comprising relatively movable piston and cylinder members, said piston member having longitudinal passage means and radially extending ports formed therein for communicating the opposite ends of the cylinder, a spring biased check valve normally closing said passage means, an actuator assembly located in said piston member in axial alignment with the check valve for moving the latter to a first position wherein a predetermined flow rate between the ends of the cylinder is provided and to a second position wherein a flow rate greater than said predetermined flow rate is provided, said actuator assembly comprising a fluid actuated primary plunger engaging the check valve and adapted to move said valve to said second position, a fluid actuated secondary plunger engaging the primary plunger and adapted to move the latter a distance whereby said valve is moved to said first position, first and second conduit means provided in said piston member for respectively communicating pressurized fluid to one side of said primary and secondary plungers, a hydraulic circuit for supplying pressurized fluid to one end of said jack whereby said implement is raised, said circuit including first and second solenoid operated valve assemblies between said pressurized end of said jack and said first and second conduits, and control means for selectively energizing said solenoid operated valve assemblies whereby pressurized fluid from said pressurized end of said jack is directed to one of said conduits to cause said check valve to be opened so that the implement will drop by gravity.

9. In combination with an earth-moving scraper having a bowl movable between a raised and lowered position, a single-acting hydraulic jack supporting said implement for movement between said positions, said hydraulic jack comprising relatively movable piston and cylinder members, said piston member having longitudinal passage means and radially extending ports formed therein for communicating the opposite ends of the cylinder, a spring biased check valve normally closing said passage means, an actuator assembly located in said piston member in axial alignment with the check valve for moving the latter to a first position wherein a predetermined flow rate between the ends of the cylinder is provided and to a second position wherein a flow rate greater than said predetermined flow rate is provided, said actuator assembly comprising a fluid actuated primary plunger engag:

ing the valve and adapted to move said valve to said second position, a fluid actuated secondary plunger engaging the primary plunger and adapted to move the latter a distance whereby said valve is moved to said first position, first and second conduit means provided in said piston member for respectively communicating pressurized fluid to one side of said primary and secondary plungers, a hydraulic circuit for supplying pressurized fluid to one end of said jack whereby said bowl is raised, said circuit including first and second solenoid operated valve as-i semblies between said pressurized end of said jack and said first and second conduits, and control means for selectively energizing said solenoid operated valve assemblies whereby pressurized fluid from said pressurized end of said jack is directed to one of said conduits to cause said check valve to be opened so that the bowl will drop by gravity.

10. In combination with an earth-moving scraper having a bowl movable between a raised and lowered position, a single-acting hydraulic jack supporting said implement for movement between said positions, said hydraulic jack comprising relatively movable piston and cylinder members, said piston member having longitudinal passage means and radially extending ports formed therein for communicating the opposite ends of the cylinder, a spring biased check valve normally closing said passage means, an actuator assembly located in said piston member in axial alignment with the check valve for moving the latter to a first position wherein a predetermined flow rate between the ends of the cylinder is provided and to a second position wherein a flow rate greater than said predetermined flow rate is provided, said actuator assembly comprising a fluid actuated primary plunger engaging the valve and adapted to move said valve to said second position, a fluid actuated secondary plunger engaging the primary plunger and adapted to move the latter a distance whereby said valve is moved to said first position, first and second conduit means provided in the rod portion of said piston member for respectively communicating pressurized fluid to one side of said primary and secondary plungers, a hydraulic circuit including a pump and control valve for supplying pressurized fluid to one end of said jack whereby said bowl is raised, said circuit including first and second solenoid operated valve assemblies between said pressurized end of said jack and said first and second conduits, and electric control means for selectively energizing said solenoid operated valve assemblies whereby pressurized fluid from said pressurized end of said jack is directed to one of said conduits to cause said check valve to be opened so that the bowl will drop by gravity.

References Cited UNITED STATES PATENTS 2,902,007 9/1959 Rockwell 9l422 X 3,093,116 6/1963 Rood 9l422 X 3,127,688 4/1964 Hein et al. 37l29 ABRAHAM G. STONE, Primary Examiner.

A. E. KOPECKI, Assistant Examiner. 

1. IN COMBINATION, A HYDRAULIC JACK COMPRISING RELATIVELY MOVABLE PISTON AND CYLINDER MEMBERS, SAID PISTON MEMBER HAVING PASSAGE MEANS FORMED THEREIN FOR COMMUNICATING THE OPPOSITE ENDS OF THE CYLINDER, A SPRING BIASED CHECK VALVE NORMALLY CLOSING SAID PASSAGE MEANS, AN ACTUATOR ASSEMBLY LOCATED IN SAID PISTON MEMBER FOR MOVING SAID CHECK VALVE TO A FIRST POSITION WHEREIN A PREDETERMINED FLOW RATE BETWEEN THE ENDS OF THE CYLINDER IS PROVIDED AND TO A SECOND POSITION WHEREIN A FLOW RATE GREATER THAN SAID PREDETERMINED FLOW RATE IS PROVIDED, SAID ASSEMBLY COMPRISING A PRIMARY PLUNGER ENGAGING THE CHECK VALVE AND ADAPTED TO MOVE SAID VALVE TO SAID SECOND POSITION, A SECONDARY PLUNGER ENGAGING THE PRIMARY PLUNGER AND ADAPTED TO MOVE THE LATTER A DISTANCE WHEREBY SAID VALVE IS MOVED TO SAID FIRST POSITION, AND MEANS FOR SELECTIVELY ACTIVATING SAID PLUNGERS. 